Dave has been a tree guy all his life. He started as a young man clearing tree damage in the wake of Hurricane Hazel; he went on to become the parks supervisor for North York.

He is a certified arborist, one of the first; he is also the guy who designed the tree inventory system that is the standard across North America.

He lives on a wide, quiet street graced with lovely trees. In his front yard, a big blue spruce; in his back yard a couple of maples, a larch, a locust, several more spruce trees and some cedar. He planted all but two, and he pruned them all with professional care. Guess what?

No damage to speak of.

He talked of the days when he moved from parks to become North York’s arborist resource officer; his job was to make sure that trees were not killed needlessly during the infill housing boom.

He said, “You couldn’t get a building permit until a tree survival guarantee was in place. I’d go out and apply a tree valuation. The builder would have to give the city a cheque for that amount, returnable when the job was done and the tree was determined to be healthy. At one time, I had a million dollars on deposit.”

That’s real power.

And this is the heart of the matter: “Trees have esthetic value, they affect property value, they are advantageous to human beings. The loss to the city is not just a tree that was killed; there’s an esthetic loss that can be measured.”

How do you measure beauty?

“You take a tree with a 10-inch (25 cm) diameter, dig it up and move it, replant it and record all the costs. You take the diameter at breast height, determine the number of square inches in the cross section, and divide that into the cost of moving to get a cost per square inch.”

That gives you the value of a perfect tree, in perfect condition, in the perfect spot.

But perfection is a moving target; some species are more valuable than others; the health and condition of a tree is a factor in its worth; a prominent tree has more value than a tree hidden in the back; a tree with a glorious crown beats one that is lacking; and so on.

And so you start from perfection and begin a process of reduction for each of these factors. A perfect tree might be worth, say, $20,000, but when you start knocking off points for imperfection, the true value might only be $1,000.

Dave reads the paper as closely as you do; if Toronto has lost 20% of its tree canopy, as has been reported, then according to his calculations the esthetic loss is worth some 1.6 billion dollars.

Yikes.

He took me outside to illustrate a point. Up and down his street, beauty everywhere and no tree damage to be seen. Why?

Because his neighbours were smart enough to consult him over the years, and there has been trimming, and the trees are perfect, beautiful and undamaged.

There is another way to prove what he says, but it would take more time than I’ve got: A person could survey all the trees pruned in the city in recent years, and compare them to ones we neglected.

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